Method of distributing molten glass gobs in an IS machine

ABSTRACT

A method of distributing molten glass gobs in an IS machine whereby gob scoops are positioned beneath associated gob discharges for motion independently of each other. Each scoop is driven by a three-phase electric servo motor to swing through an arc independently of the other scoops while maintaining a position beneath the associated gob discharge. Synchronization of the motors to the operation of glass forming molds of the IS machine is accomplished by coupling a first sensor to each motor to provide a signal indicative of the actual position of the motor, generating a varying signal indicative of a desired position of each scoop, generating a command signal for each motor as a function of the difference between the signal indicative of the desired position of the scoop and the signal indicative of the actual position of the motor, applying the command signal as first and second torque commands to two phases of the three-phase motor, and applying a third torque command to a third phase of the three-phase motor as a function of the sum of the associated first and second torque commands.

This application is a division of application Ser. No. 08/066,189 filedMay 24, 1993, now U.S. Pat. No. 5,405,424.

The present invention is directed to manufacture of glass articles suchas containers, and more particularly to an improved method and apparatusfor distributing gobs of molten glass among a plurality of mold stationsor sections.

BACKGROUND AND SUMMARY OF THE INVENTION

Glass containers are conventionally formed in a machine that comprises aplurality of sections, in each of which there are one or more blank orparison mold cavities and transfer mechanisms that are synchronized witheach other. This machine, called an individual section or IS machine,receives glass in the form of discrete mold charges or gobs. Moltenglass from a furnace is cut into individual gobs, which are fed to a gobdistributor. The purpose of the gob distributor is to distribute thegobs to the individual sections of the IS machine in the appropriatesequence in such a way that the glass gobs simultaneously arrive at themold cavities in each section in sequence. U.S. Pat. Nos. 3,585,017 and3,597,187, and patents noted therein, illustrate the general technology.

U.S. Pat. No. 2,859,559 discloses a gob distributor construction inwhich a scoop is disposed beneath a gob shear mechanism for receivingmolten gobs in sequence, and is coupled by a shaft to a motor forfeeding the individual gobs to spaced chutes or troughs. Each troughleads to the initial mold cavity of an associated section of an ISmachine. Each cavity of the IS machine has an associated trough, and thescoop feeds gobs to the individual troughs in an appropriate sequence.U.S. Pat. No. 3,597,187 discloses a gob distributor in which a pluralityof scoops each have an upper end disposed beneath an associated gobdischarge, and a lower end disposed to swing through an arc adjacent toa corresponding plurality of troughs. Each scoop is carried by a scoopsupport frame, which is in turn is coupled to a drive shaft. Themultiple drive shafts are coupled to a gear transmission drive, in whichthe shafts are conjointly driven through associated gears by a singlemotor. Although this transmission drive arrangement maintains propersynchronism among the scoops, a problem arises when it is desired tochange the number of scoops. An entirely new transmission drive isrequired.

A general object of the present invention is to provide a glass gobdistribution system and method in which gob distribution scoops may bereadily added, deleted or inactivated without requiring redesign orreplacement of the entire scoop drive structure. Another and morespecific object of the present invention is to provide a glass gobdistribution system and method for a multiple-cavity IS machine in whichthe scoop for each cavity is mechanically independent from the scoopsfor the other cavities, and in which scoop position and motion profilemay be readily electronically adjusted independently of the other scoopsof the distribution system.

A molten glass gob distributor for a glass article manufacturing systemin accordance with the present invention includes a plurality of gobdischarges, and a plurality of scoops for receiving gobs from each suchdischarge and distributing the gobs among a plurality of troughs orchutes leading to associated molds in a multiple-cavity IS machine. Eachscoop is mounted to rotate about a fixed axis with the upper endremaining positioned beneath the associated gob discharge while thelower end swings through an arc adjacent to the associated troughs. Aplurality of electric motors are individually coupled to each associatedscoop for selectively and individually rotating the scoops. The electricmotors are all connected to a motor controller for synchronizingoperation of the motors and rotation of the scoops to each other and tooperation of the forming machine. Preferably, the motors compriseelectric servo motors each individually coupled to a single associatedscoop, and the motor controller comprises an electronic servo motorcontroller operatively coupled to each servo motor and synchronizingoperation thereof by means of a synchronizing input from the formingmachine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features and advantagesthereof, will be best understood from the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a fragmentary perspective view that illustrates a molten glassgob distribution system in accordance with one presently preferredembodiment of the invention;

FIG. 2 is a functional block diagram of the gob distribution systemillustrated in FIG. 1;

FIG. 3 is a functional block diagram of each motion controllerillustrated in FIG. 2; and

FIG. 4 is a graphic illustration of motion profile for each scoop,illustrating sequence of delivery of mold charges or gobs to the eightsections of an IS machine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 illustrates a gob distribution system 10 in accordance with onepresently preferred embodiment of the invention as comprising threearcuate scoops 12,14,16 each having an upper end positioned beneath anassociated glass gob discharge orifice 18,20,22. Each scoop 12,14,16 iscarried by an associated support bracket or frame 24,26,28 to rotatethrough an arc about a fixed axis such that the upper end of each scoopremains positioned beneath the associated gob discharge orifice, whilethe lower end of each scoop swings through an arc adjacent to anassociated array of troughs or chutes 30,32,34. The number of troughs ineach array 30,32,34 is determined by the number of sections 35 in the ISmachine. The number of scoops 12,14,16, the number of orifices 18,20,22and the number of trough arrays 30,32,34 are all determined by thenumber of molds or cavities in each section 35 of the IS machine. Forexample, three gob orifices, scoops and chute arrays are illustrated inFIG. 1 for use in connection with a so-called triple-cavity IS machinein which each section 35 includes three parison molds 35a, 35b and 35c.A typical IS machine may include eight such machine sections 35, so thateach chute array 30,32,34 would include eight individual chutespositioned for alignment with the corresponding scoop 12,14,16, of whichonly three chutes are illustrated in FIG. 1 for purposes of clarity. Thegeneral purpose of gob distribution system 10 is to deliver glass moldcharges or gobs to the three molds 35a, 35b, 35c simultaneously for eachmachine section 35 in sequence. To the extent thus far described, system10 is of generally conventional construction.

In accordance with the present invention, each of the scoop supports24,26,28 is coupled by an associated drive shaft 36,38,40 to a gear box42,44,46 (FIGS. 1 and 2) driven by an associated electric servo motor48,50,52. Each servo motor 48,50,52 receives drive signals from acorresponding servo amplifier 54,56,58 under control of an associatedmotion controller 60,62,64. A first position sensor R1, such as aconventional resolver, is coupled to each servo motor 48,50,52 forproviding to the associated motion controller 60,62,64, an electricalsignal indicative of angular position of the associated motor driveshaft. A second position sensor R2, such as a conventional resolver, iscoupled to each gear box 42,44,46 for providing to the associated motioncontroller 60,62,64 a second electrical signal indicative of absoluteposition of the associated scoop 12,14,16. The several motioncontrollers 60,62,64 are coupled by a communications link 66 to asupervisory controller 68. Supervisory controller 68 receives asynchronizing input from an infrared sensor 70 positioned adjacent to aselected one of the gob orifices 18,20,22 (FIG. 1) to provide acorresponding signal when a glass gob is discharged from the orifice.Supervisory controller 68 is also connected to an operator interface 72,such as a keyboard and screen, for receiving calibration and adjustmentinputs, etc., and providing output for display to a machine operator.Supervisory controller 68 and motion controllers 60,62,64 also receivesynchronizing master clock and master reset inputs from IS machine 35.

In operation, each motion controller 60,62,64 receives from supervisorycontroller 68 and stores in internal memory a table of data indicativedesired position profile 74 (FIGS. 3 and 4) at the associated scoop. Forexample, FIG. 4 illustrates a profile 74 for an eight-section machine inwhich each scoop is cycled through chute positions 1,5,4,8,3,7,2 and 6in a continuing sequence for distributing glass gobs simultaneously tothe three parison molds of each machine section in that sequence. Withineach motion controller 60,62,64, the profile 74 for the associated scoopis compared to the position feedback from the associated resolver R1,with the difference or error generating an absolute torque command 76(FIG. 3). This torque command is commutated at 78 for power phases A andB applied to the associated amplifier 54 (or 56 or 58). The torquecommand for the third phase is calculated in the associated amplifier asthe sum of the torque commands for the first and second phases. Thesetorque commands are applied by the amplifier to the associated servomotor to drive the gear box and scoop to the desired scoop position.

The resolvers R2 indicate absolute position for each scoop. Thisposition information is employed during system initialization todetermine actual position of each scoop, which is fed to supervisorycontroller 68. The supervisory controller may then command each motioncontroller to move its associated scoop to a defined initial or "home"position. After this initialization sequence, the absolute positionoutput of resolvers R2 may be monitored periodically to correct anydrift in scoop position.

It will be readily appreciated that the electric motor and motor controlgob distribution system 10 illustrated in the drawings represents adistinct advantage over the prior art gear transmission drivearrangements discussed above. The several scoops 12,14,16 aremechanically completely independent of each other, so that position ofeach scoop may be calibrated and controlled completely independently ofall other scoops. For example, position of scoop 12 at any point in itsprofile 74 may be readily adjusted by means of operator interface 72,supervisory controller 68 and motion controller 60 without in any wayaffecting motion or position at any of the other scoops. Motion andprofile of each scoop may be adjusted during system operation. Scoopsmay be added, deleted or simply rendered inoperative by addition ordeletion of associated servo motors and motion controllers etc. withoutrequiring complete replacement or major rework of a gear drivetransmission. For example, FIG. 2 illustrates addition of a fourthmotion controller 80 with associated amplifier 82, motor 84, gear box 86and scoop 88.

If the overall speed of the glass forming machine must be increased,supervisory controller 68 may automatically reduce the allowable timefor motion of the various scoops, and adjust the motion profilesaccordingly so that the dwell times during which each scoop is alignedwith a chute remains constant. The same profile 74 would normally beused for each scoop, but a unique profile that accommodates uniquedesign considerations or minor dimensional variations between or amongchutes may be readily accommodated. The scoops would normally besynchronized to operate at the same time, moving into and out ofposition at the same time. However, here again differences may bereadily accommodated by electronic adjustment because each scoop iselectronically controlled independently of the other scoops. Scooppositions may be determined and set during installation by moving thescoops into alignment with each of the troughs in turn and storing thecorresponding position information in memory. The master clock andmaster reset signals from IS machine 35 are employed for primarysynchronization purposes, with infrared sensor 70 providing back-up.

We claim:
 1. A method of distributing molten glass gobs from a pluralityof gob discharge means among a plurality of glass article forming molds,said method comprising the steps of:(a) positioning a gob scoop beneatheach of said plurality of gob discharge means for motion independentlyof each other, (b) driving each said scoop with an associatedthree-phase electric servo motor including a motor drive shaft to swingthrough an arc independently of other said scoops while maintainingposition beneath the associated discharge means, and (c) synchronizingoperation of all of said motors to operation of said glass articleforming molds by: (c1) coupling a first sensor to each said motor andproviding from each said first sensor a signal indicative of an actualposition of the motor drive shaft of each said motor, (c2) generating avarying signal indicative of a desired position of each said scoop, (c3)generating a command signal for each said motor as a function of adifference between the signal indicative of the desired position of theassociated scoop and the signal indicative of the actual position of themotor drive shaft of the associated motor, (c4) applying said commandsignal as first and second torque commands to two phases of saidassociated three-phase motor, and (c5) applying a third torque commandto a third phase of said associated three-phase motor as a function ofthe sum of the associated first and second torque commands.
 2. Themethod set forth in claim 1 comprising the additional steps of:(d)coupling a second sensor to each said scoop to provide a signalindicative of actual position of the associated scoop, and (e) uponinitialization of operation of said method, employing said signal fromsaid second sensor to move the associated scoop to an initial position.3. The method set forth in claim 2 comprising the additional step of:(f)monitoring said signal from said second sensor during said step (b) and(c) to correct any drift in the position of the associated scoop.